If they play safe, it might be something based off the Spirit Healer. It would make sense, something along the line of Deathwing raid so hard you'll be wiping forever, so dead priest aka spirit healer.

I have been awaiting a spirit healer armor set for years, I am completely with you on this.

+ 1 holy sets for priests, kinda like T3. Shadowform will take care of the shadow look. Even better would be when you turn on shadowform, instead of the purple glow, all the armor "magic" (for example flames in T12) change from "holy color" to "shadow color".

Obviously we are getting a shower curtain for T13. And a plunger for a weapon. In all seriousness, making it for holy/disc and let "shadowform" do the rest is a terrible idea. They should make the tier around shadow and let holy/disc bitch about it. See it's not so nice to feel left out...

Honestly i don't see how any issues can be found with shadow priests and the look of gear. Shadowform makes it look like shadowgear so there's no issue, that white light on the shoulders turn dark so there's your "shadowy" look.

Speaking on topic of the tiers look i'm guessing it's gonna be something involving either the twilight cult like many have said about Benedictus, or if they use the dragonflights then it'd probably be either twilight dragons or the red's.

I actually think the priest Ulduar Tier was amazing for priests. The naxx one did have wings which i thought was amazing but the way they made it viewed was rediculous from behind cause it made it look like your wings were retarded and going the wrong way. The warlock wings from their tier(forgot the number) was amazing and something like that would be cool for priests too since we are kind of connected with angelic shit, spirit of redemption, guardian spirit, etc.